Computing platforms can potentially be compromised through attacks and malware infections, where the likelihood of compromise increases with the degree of threat exposure as well as with the number and the severity of vulnerabilities in and around the computing platform. There will always be a certain likelihood of compromise, because vulnerabilities can never be completely eliminated, and threats can never be fully neutralised.
IT applications can have different sensitivity levels, and different activities will expose computing platforms to different threat levels. Example of high sensitivity applications are online banking and management of access credentials such as passwords. Examples of activity with high threat exposure are accessing unknown web sites and installing unknown external devices such as USB plug-in drives, in which cases there is a relatively high likelihood that the computing platform can be attacked and compromised in some way, which in turn could negatively affect the security of sensitive applications. It is therefore not desirable nor advisable to use the same computing platform both for high sensitivity applications and for engaging in activities affected by high threat exposure.
Ideally, two separate platforms should be used, where one is used for sensitive applications and the other for activities with high threat exposure. By using different computing platforms exclusively for different environments and for different applications, the likelihood of an attack originating from an environment of high threat exposure spreading to and compromising a high sensitivity application is reduced.
Another good reason for using multiple separate computing platforms is that they can cross-check each others' integrity. In case one computing platform is compromised, this situation can be detected and possibly corrected by the other computing platform. In an architecture where one computing platform is used to cross-check the integrity of another computing platform it would be necessary for attackers to compromise both computing platforms in order to execute a successful attack. This method of multi-factor security obviously leads to more robust security and reduces the likelihood of successful attacks.
However, people typically use the same computing platform for both, which is problematic. This is because handling multiple devices can be relatively cumbersome, resulting in poor usability. For example, users would have to procure and manage multiple devices, which in case of mobile computing would have to be carried around.